…ader
and the routing header, based on rfc2292bis-02.
this part was disabled when merging a recent mip6 patch from ericsson,
without much consideration about the rationale. Actually, disabling this part
just for MIP6 convenience is a bad idea (or at least not a good idea).
We need to think carefully about a way to make the advanced API coexist with
MIP6 options.

from myself, if the interface is !IFF_SIMPLEX. multicast packets
are explicitly copied via loopback interface in ip_output() and
ip6_output(), so the old codepath caused a duplicate. also the
old codepath affected IPv6 DAD. KAME PR 360